Four people have been detained and charged in Chicago over a “sickening attack” on a bound and gagged man that was broadcast live on Facebook.

The victim has been identified as a Chicago resident who police said had mental health issues.

“It makes you wonder what would make individuals treat somebody like that,” Superintendent Eddie Johnson told reporters.

The video appeared to show someone using profanities about “white people” and President-elect Donald Trump. Photo: Facebook.

He described the video as “sickening”.

Prosecutors filed hate crime and aggravated kidnapping charges against the four black suspects.

Eighteen-year-olds Jordan Hill, Brittany Covington, Tesfaye Cooper and 24-year-old Tanisha Covington were also charged with aggravated unlawful restraint and aggravated battery with a deadly weapon.

Three have been charged with residential burglary.

The video, obtained by Chicago media outlets, appeared to show someone off-camera using profanities about “white people” and President-elect Donald Trump.

Chicago police said authorities were considering whether the attack falls under hate crimes statutes.

Spokesman Anthony Guglielmi said the four suspects made “terrible racist statements” during the assault, but police believe the victim was targeted because he has “special needs,” not because of his race.

Mr Guglielmi said it was possible the suspects were trying to extort something from the victim’s family.

A still from the video showing the man with his mouth taped shut as a woman and other people cut off his shirt and hair with a knife. Photo: AAP/Twitter.

The investigation began on Monday after officers found a man who “was in distress and was in crisis” walking on a street on Chicago’s west side.

The man was taken to a hospital and it was later discovered he had been reported missing from an unidentified suburb.

At about the same time, police took several people into custody at a nearby address where they found signs of a struggle and property damage.

Investigators determined that the missing man had been at the same address.

Watch the footage here. WARNING: the video contains graphic footage and offensive language.